The present invention is related to a gear box for a kneading machine which allows coupled oscillation and rotation from a single drive wherein the oscillation strokes per revolution is adjustable but invariant at a given adjustment. More specifically, the present invention is related to an adjustable eccentric which allows for fine tuning of the oscillation amplitude or stroke length.
Kneading machines are widely used in a variety of applications. In general, kneading machines can be categorized as either rotational only or rotational and oscillatory. The present application is related to a kneader capable of rotating and oscillating which is also referred to in the art as a reciprocating kneader.
A critical design feature of a reciprocating kneader is the relationship between the rotation and the oscillation. For convenience in the art this is referred to as “stroke ratio” which is the number of oscillations, or translations parallel to the rotational axis, per rotation of the axis. For example, a stroke ratio of 1 would indicate that the oscillation starts at an initial point, moves through the entire range of motion and returns to the starting point during a single rotation. The range of motion is referred to as “stroke length”. With a stroke ratio of 2 the oscillation would occur twice with a single rotation. The stroke ratio can be a whole number or in some instances it may be a fraction, such as 2.5, wherein five oscillations would occur with two rotations.
The screw design and, if present, pin arrangement, define the stroke ratio and stroke length requirements of a reciprocating kneader. If the stroke ratio and stroke length is not matched to the screw design and pin arrangement the screw flights and pins may collide in catastrophic fashion. As a result, reciprocating kneaders have been considered relatively inflexible with regards to design changes. Reciprocating kneaders are typically designed for a specific application and the design choice often limits the materials which can be kneaded in an existing kneader.
As would be realized the rotation and oscillation can be adjusted by using separate drive mechanisms yet this approach has a high failure rate. If one drive mechanism varies, even slightly, the rotation and oscillation lose their synchronous motion which leads to collisions of flights and pins with catastrophic results. Therefore, it is highly desirable that the rotation and oscillation have a common drive to avoid the potential for stroke ratio variability.
It has been a long standing desire to provide a reciprocating kneader wherein the stroke ratio can be easily modified thereby allowing for variations in the combination of screw and pin. This would allow a single unit to be used for many different applications simply by inserting a different screw, using a different pin arrangement and adjusting the stroke ratio and stroke length in accordance with the choice of screw and pin. Unfortunately, such equipment has been limited by the lack of a suitable gearbox.
U.S. patent Ser. No. 12/857,001 filed Aug. 16, 2010, which is incorporated herein by reference, provides a gear box wherein the stroke ratio is constant regardless of the rotation rate of the reciprocating kneader. Even though this represents an advance in the art the stroke length is not easily adjusted to account for manufacturing tolerances which has thwarted full implementation of the gear box.